A cosmetologist is selecting a relaxer for a client with resistant virgin hair versus a client with fine, color-treated hair. Which statement correctly compares thio (ammonium thioglycolate) relaxers to hydroxide relaxers?
- AHydroxide relaxers and thio relaxers use the same chemical mechanism but differ only in fragrance
- BThio relaxers work by breaking disulfide bonds through reduction, while hydroxide relaxers work through lanthionization
- CThio relaxers use a higher pH than hydroxide relaxers and always require a neutralizing shampoo
- DThio relaxers are stronger and used only on resistant gray hair
Show answer & explanationAnswer & explanation
Correct answer: B. Thio relaxers work by breaking disulfide bonds through reduction, while hydroxide relaxers work through lanthionization
Thio relaxers straighten hair by reduction, breaking disulfide bonds (similar to a perm) without converting them, and require an oxidizing neutralizer; hydroxide relaxers work through lanthionization, converting disulfide bonds into stable lanthionine bonds permanently, requiring only a neutralizing shampoo, not an oxidizer.
Why the other options are wrong
- A. The two relaxer types use fundamentally different chemical mechanisms, not just fragrance.
- C. Thio relaxers actually have a lower pH than hydroxide relaxers (about 9.6-10.4 vs 12-14).
- D. Thio relaxers are typically gentler and used on fine or delicate hair, not resistant gray hair.
Thio vs Hydroxide Relaxers
Thio relaxers straighten hair via reduction (breaking disulfide bonds, requiring oxidizing neutralizer), while hydroxide relaxers permanently convert disulfide bonds into lanthionine bonds (lanthionization).
- Thio relaxer pH ~9.6-10.4, needs oxidizing neutralizer
- Hydroxide relaxer pH ~10-14, uses lanthionization
- Hydroxide changes are irreversible; thio bonds are reformed differently
Memory trick: Thio reduces like a perm; hydroxide permanently rewires the bond into lanthionine steel.